"But the worst is the very unregulated dosage. Three "sprits" just does not
work with me. "

One of the things I spent a bunch of time looking at was how to get a reproducible "sprit."  The trigger on foggers is simply connected to a small pump.  So, at least in theory getting a constant output per squeeze on the trigger should be easy.  It was not.  The first thing I learned was a fast squeeze on the trigger delivered a much larger amount of liquid than a slow squeeze.  I also learned that water solutions are poor lubricants and as a result the trigger did not fully return to the neutral position.  I had to drill a hole in the top of the fogger handle so I could push the trigger back to full neutral.  A stronger return spring would solve this issue but the spring the manufacturer puts in the fogger is strong enough that after you have squeezed the trigger 100 times you do not want a stronger spring.  This trigger problem was considerably less of an issue with ethanol.

At any rate, by practicing cold shots with the fogger not even lit I found with practice I could deliver a consistent 1.2 ml shot per trigger squeeze with the particular fogger I was using.  I am sure that volume would vary from unit to unit and person to person as it is quite sensitive to how fast you squeeze that trigger.  It is easy enough to calibrate.  Just squeeze until liquid comes out the nozzle with the fogger not lit and then capture a few squeezes and measure the delivered volume.

With water one thing I noticed was some of the water did not get vaporized and left a wet spot in the floor of the hive.  Obviously all the oxalic acid in unvaporized water is also unvaporized and probably 100% ineffective.  It looked visually like this unvaporized water was a minor part of the total water delivered.  But, I made no attempt to quantify the amount.  I did show you could capture the "fog" in a large plastic bag and test for oxalic acid and show there was lots of undecomposed oxalic acid left.  So, even thou the fogger tubes are red hot the oxalic acid is not all broken down and lost.  Also, when using water solutions you really do not get a fog.  You get some liquid and a lot of vapor.  The vapor is below the dew point it seems so does not form a fog like you see with mineral oil or glycerin.  Either the particles of oxalic acid produced are so small they do not scatter light or else the oxalic acid is not desubliming either as it does not give a visible fog.  I suspect the former.  Such a small particle size might be ineffective as such particles are so small they could well simply stay suspended in air and eventually get swept out of the hive by natural air currents.

Another factor is temp recovery of the heated fogger tubes.  They run red hot.  Yet, if you squeeze that trigger several times close together you can see the tubes cooling down by the color change.  With water I was waiting for a count of 20 between squeezes to allow temperature recovery.  If I went faster than that I could tell I was getting less vaporization by the change in the sound of the whoosh when I squeezed the trigger.  Even ethanol needed about ten seconds between squeezes for temp recovery.  With water I needed ten trigger squeezes to treat a nuc.  That is a treatment time of about three minutes per hive.  That is not even fast.

All in all, compared to the alternative proven oxalic acid methods a fogger is not that fast and easy.  And water solutions proved ineffective at mite control.

Dick

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